If you need all the features of Gmail or Inbox, probably not. If you can get by with what IMAP has to offer, FastMail has been very solid for me. I pay about $50 a year for a single account, which can support lots (unlimited?) domains and addresses (both sending and receiving). The web UI is nice, and the iOS app is pretty good, too. They also blog a lot about what they are doing on the technical side, and seem really invested in the future of IMAP and open source. They have a serious focus on speed. Spam filtering I would say is like a B-, there are some really obvious things that seem to get through no matter how much I train it. Support staff has been helpful when I've needed it, though.
They are excellent! I had a feature request twice, it was implemented on their beta server within days. Their (standard-conforming) IMAP and Webmail is really fast (they cache recent stuff on SSDs). They have apps now for Android and iOS (basically wrappers around the web app with notification support, but they work well enough). They recently added CalDAV and CardDAV support.
On top of all of that, they actively contribute to open source projects such as Cyrus.
Thanks for the suggestion, I like what they're offering. I hadn't considered spam, probably because gmail is so good at it that I haven't thought about spam in years. Anyway, seems worth a shot.
edit: just remembered they have a referral system, should you be interested: http://www.fastmail.com/?STKI=13352501