So, my GMail-based setup is certainly nowhere near as good as what I had on DreamHost. I had much better control of my spam filter (bogofilter+spamassassin) on DH, and never, ever got 419 scams in my inbox (unlike on GMail where it seems like several make it through every day), and meanwhile GMail's filter seems to be overprotective on things like topic reply notifications and the like (so I keep having to check my spam box and adding whitelist rules). Plus, bogofilter's yes/no/unsure classifications made checking the spam filter much easier since I never, ever had to check the 'yes' folder (300 messages/day) for false-positives (I just had to guide it on the maybes, with around 10 messages/day).
The more annoying thing by far, however, is the limit to the number of simultaneous IMAP connections. Between my computer at work, two computers at home, and my iPhone (which often decides to connect over EDGE even when I'm in WiFi range — and, amusingly enough, there's a few open access points it seems to connect through while I'm riding my bike to work, according to GMail's access log) I hit the limit pretty quickly, and unfortunately, GMail handles the limit by killing the most recent ones — meaning the one I'm actually using is the one that's most likely to start messing up. (It doesn't help that when I'm at work I'm using Thunderbird which seems to be much more aggressive about its reconnect attempts than Mail.app, which only makes things mess up even faster. I've also run into trouble with Thunderbird locking me out of my corporate email due to repeated login failures, which is one of the reasons I'm back to using Outlook.)
Basically, email sucks.