Formality is something many Pagans lack when we interact with deity. Informality can be wonderful, too - even the most staunch ceremonialist must at times, one feels, sit back with a drink and speak at leisure with their gods. Some are lucky enough to have set, specific formal rituals that are properly followed, as in Wicca. Many groups, even those that are eclectic, create rituals that are quite formal in construct. My own rituals tend to be a mix of formality and informality - one following the other as the business of the rite is dealt with and the sitting and chatting over a warm glass of mead comes to the fore.
But outside of ritual, most of us have no written prayerbooks to depend upon (while a couple of quite good ones have been published, they cater to a specific religion, or a specific flavour of eclecticism). Hellenic Polytheists, of course, are lucky to have the Homeric and Orphic hymns at their disposal when they feel like offering formal prayer to a deity - and often have some to choose from. For others, they may have to form their own with references from lore. There are few Pagan religions with a book of hours or book of common prayer to fall back upon when words fail one, or lend some structure or formality to one's prayer.
I believe that formal prayer has value. That daily devotionals have value. There is something of a movement away from formal prayer in Paganism, possibly on the basis that we tend to have quite close, personal relationships with our deities. Why bother with formality if we can have a friendly chat? It's still respectful (at least, I hope) and it's more personal. I value informal prayer as well, as I mentioned; those informal chats are important too. Formal prayer, however, speaks to us as well as the gods and on a level we may not consciously appreciate.
I think I'll define formal prayer here as a prayer that has an element of cultus. Cultus is an observable act or element within a religion, so a prayer with cultus would be one someone else would recognise as prayer or religious action. It's not something, in other words, one can do sitting on the bus. Perhaps one chooses to light a candle, or kneel at one's bedside... to clasp his hands above one's dinner plate as one says grace or to leave an offering at a shrine, an altar, at the foot of a tree. One might read a rosary or set of prayer beads, or sing a chant. All these may be formal prayer; in this instance, I'm referring to formal prayer with an element of repetition.
The element of repetition may be the time of day, the place, the form in which the cultus takes. The prayer needn't be necessarily the same words each time. One person may write a different prayer for each day of the week, another might write an opening or a closing (or both) and speak from the heart between the two. Another person might simply speak their deity's name and pray without words. You don't have to use fancy words unless it appeals to you.
There's a monastic sort of inner stillness that repeated prayer and repeated devotion can bring. Simply lighting a candle and standing or kneeling before an altar can indicate to your mind and even your body the beginning of a sacred moment, a sacred communication. You are focused on your deity (or ancestor, or spirit, or other entity worthy of your prayer or observance). When repeated daily you can surprisingly quickly become conditioned to becoming calm and focused and of a spiritual mind, and simply standing in front of your altar may convey to you a sense of that stillness.
Concepts like "Pagan Monasticism" very much appeal to me - to a point - and I'll write up a post on it later. I've heard it mentioned by quite a few people now with a kind of yearning - a yearning for that structure, that stillness, that ability to focus solely on studying one's religion and serving one's god for even a short length of time.
Of course, while it would be nice to escape the world for a month and rush off to a monastery every time we felt the need, it's not a possible thing for us. Not at this point, anyway. Incorporating a moment of that structure and that stillness is often all we can manage. But it's worth making the effort.
The danger of repeated prayer and repeated cultus is that it may lose all meaning, and become repeated actions or words with no feeling behind them. Not every prayer will be truly satisfying and occasionally the best of us will rush through it with our minds on something else. The unsatisfying ones are more than made up for by the ones that take your breath away. But if you find yourself rushing through it more times than not, it may be time to change it. Stop. Try something else. You may keep your prayer informal for a week to give yourself a break, and return to your formal prayer to realise with a start how much you had missed it. Or you may find yourself rewriting it entirely. A Pagan's personal practices and beliefs may change over time and prayers should change to reflect those changes.
Most of all, it deepens our relationships with our deities. Formal prayer allows - and aids - us to concentrate on our deities, to offer our time and our love to them in a formal, quiet, still and sacred moment.
I've heard it mentioned by others that there's a movement within Paganism away from prayer itself. I was quite taken aback to hear this; non-theistic Pagans aside, why would you not communicate with your deity? It may be some form of backlash against unfortunate experiences with a previous religion, or perhaps misunderstanding on how the word "prayer" is used - some people associate it primarily with supplication. Nevertheless, I haven't run into anyone like this myself. Just looking at interest in prayer books and prayer beads, I think it's well-valued in Paganism, and growing more so. As it should.