I've had mine for a while, with very few issues until recently:
1. I didn't like how the bridge feature was removed at one point via firmware upgrades. I went to use it and it was gone, did some searches and found out DLink decided to remove it so they could sell bridge specific hardware. New features being added is never expected, but removing functionality is just wrong on the part of a manufacturer in my opinion.
2. Recent stability issues. Within the last month or so I've had wireless connections drop out for no reason, requiring reboots to the router.
3. Last summer I was getting slow WAN speeds, inconsistent connections, and just a lot of weird things happening. I had the router stacked on top of a DLink 8 Port gigabit switch and it was really warm. I switched to using the little stand keeping the router vertical and the problems instantly went away and haven't returned. I'd recommend keeping the DIR 655 vertical, and with room around it for some air to circulate because it does run a little warm.
4. Wake on Lan is just strange on all DLink routers. I don't do a lot of this, and if I did, I would get another brand router because of the strange things you have to do for it to work with a DLink.
The log can get full (it'll be pretty big though), at which point the oldest entries are dropped to make room. I've never bothered with email notifications, as I don't think you can set it up to notify when there's a problem with something, only on a schedule or when the log is full. You can view the log by logging into the web config anyway.
Overall it's been pretty solid though. When I bought it, there weren't a lot of options for gigabit lan ports and wireless N, even less that weren't priced in outer space.
If I were to buy a router today, I would look for a dual band setup, just for more flexibility. I would probably also look for one that was well supported by DD-WRT or another aftermarket firmware. The features just can't be beat going that route.