I received my Peek Pronto about 2 weeks ago and my life has changed forever since then. There were hiccups when I started because apparently Gmail and Peek were not cooperating and I was rather down about the fact that it took about 3 hours for my Peek to recognize that I even had an email in my inbox. I'm glad to say that it is pretty fast now (less than 5 minutes is fast to me) and when it does go out of service range (which is relatively rare), they pop up immediately when the service thing goes green.
I like to think of the service icon as a little man who stands there when there is barely any service and raises his arms when I get better service. I've been using www.notify.me for my RSS feeds which is not entirely filling. It gives me a tiny paragraph of information when there is one to be had (Twitter updates come as one or two lines) and just makes me want to rush to a computer w/ internet to see what's really going on. Their list of things to use with the Peek is quite long, I think. My favorite is the @snapask.com email address because I use Google's SMS and they've formatted it so that I can get relevant info when I need it. Email and push technology is going to make a lot of things useless in the future, I'm thinking.
One thing I have noticed is that when I save my settings like how much to vibrate and which sound to use, it never saves the information because as soon as I have changed the settings, nothing changes. When I called in, they said for me to either mail it to NYC to have it fixed or to buy the cable. They gave me a free month's service because of this problem, however the cost of the cable (which they mystically say is special and not to be replicated by some other random but fitting cable) was 14 something plus shipping which ended up way too close to a whole month's service anyway.
What I would love to see at some point from different people: the ability to upgrade easily (1), email Google Calendar with updates and not SMS (2), RSS feed that gives me the whole post (3), saving settings (4), and more space/sending ability. I don't want to send a photo to Posterous only to have my description of it cut off. That's super irritating.
People on the boards have suggested ping.fm for emailing to update things but I have not tried that yet. Also, it looks like a Posterous alternative and I love Posterous so it just does not go over well to me.