From what I've read Metro has actually improved somewhat since I left them a couple years ago. It sounds like they are deploying 3G in nearly all markets now (whether its via a roaming deal or their own tech I'm not sure) and the 4G coverage has also improved in terms of areas covered. As far as I know the speed is still sub-standard for 4G LTE. The highest speed test I've seen posted was in the 7Mb/s range with fairly high ping, and I get over that on my faux 4G with T-mobile. You could probably make a case that they have a better phone lineup these days than VM but most of their phones are far from high end, supposedly some better stuff is coming soon for them.
As for my personal opinion, I'd never go back to them just because of all the BS. You have to pay $3 to pay your bill, then its $5 for this and $10 for that, stuff that is free on other carriers like phone swaps. I also don't see them improving the quality of their network to compete with other carriers any time soon and for me that's a deal breaker. I need my data to work reliably and at high speeds everywhere I go and I just don't get that from Metro.