The comment on a lower end bike needing more regular fine tuning than a better quality bike I find to hold true. All my machines are running at least mid-grade components and for those it's generally a case of set it and forget it (I still regularly clean and lube). You don't need to go real high end, anything that generally lands in the middle of a manufacturers lineup, or even just a few steps up from their cheapest offering, is enough.

There's been some mention of going with something that has an internally geared hub (IGH). Sound advice and is something I'll do one of these days. If you're keen on not worrying much about maintenance, an IGH is the way to go.

I'll also hop on the flat bar suggestion train. I've been commuting for a bit now regularly with a drop bar bike, an older touring bike, and I'm not a fan of the drop bars for my short commute and tooling around town. I'll be swapping out to a flat bar soon or, more likely, a mustache bar. If you have no idea what that is, google 'mustache bar bike' and that will give you a great idea of what it is and it looks on a bike. It really gets your arms back and allows you to sit more upright.