The downside of constantly being challenged is that I'm usually exhausted at the end of the day. If I have a social event right after work, it takes me about an hour to recover from my 'code coma' and be able to make decent conversation.
Our site needs to work on Internet Explorer. Any web developer will read that and start shaking their heads in sympathy. Everyone else should just stop using IE and switch to Firefox, Chrome, or Safari. Please? You'll be glad you did.
The pay is on the low side, but there are the stock options, which hopefully will hugely make amends for that some day. Still, it would be nice to make a little more money. Every engineer knows that nice vacations and the latest electronic gadgets are a great cure for burn-out. :-)
Though the company is fairly relaxed about vacation time, the 'official' 2 weeks seems pretty minimal. (Full disclosure: I believe we should get 4-6 weeks vacation, like the more-civilized Europeans. But I'm not sure that would work in a start-up environment.)