I run two servers from discountgameservers.com and they are both fantastic.
They say they don't have any support which is technically true, however if you have a question about your server or the status of a recent steam update, I have always been able to jump on the
https://www.nfoservers.com/ IRC channel and get support that way.
The site is run by those guys to fill server space. Their servers on
https://www.nfoservers.com/ are crazy expensive because they come with amazing support, Ventrillo servers and web servers with anything over a 10 man server or something like that. The servers are exactly the same minus the extras. I havn't had any problems with their servers that I didn't create myself.
Populating a custom maps server is another issue all together. I run two servers and during peak hours for a few hours a day they are close to full. I have built a community of regulars through playtesting maps like crazy and generally giving people what they want. I opened a second server so I could move some of the more unconventinal maps off the main server. That server is now more popular during the day because for about a week I had it running achevement_idle with a reserve slot for all my members. When I went back to the normal rotation people stuck around.
My big problem now is that I want my servers populated 24/7 which is really hard with custom maps. I am planning on opening a third server that will promote a single custom map in a given week, or promote a smaller map list then the 175 map list I am running on my regular custom maps server now. This is where I will run the contest promotion when I do it.
The other big problem I hear from a lot of people is that no one donates ever. I am able to run on nearly 100% donations right now. This is really really hard to do without a community and a community cannot be had without someone maintaining and building a website. In the average day I spend at least an hour reading forum posts, being a general forum moderator (I have a handful of other forum mods) and replying to PMs. On an average Monday (when I add new maps) I spend about an hour and a half in the morning to do that before I go to work. On Tuesdays and Wednesdays (days after play tests) I spend a few hours posting feedback and demos (or just demos if I don't have a ton of time/wasn't on the server). I spend at least half an hour updating filters on my ratings page to mark test maps as test maps each weel. I have to build my main rotation list every Wednesday after the play test since I now have new ratings to base the list off of.
None of that includes time spent maintaining the server itself. Sourcemod plugins will crash the server every few months when valve updates something. People get banned that shouldn't have been. Map downloads break every once in a while.
This is what it takes to build a community. Ask Dr. Pepper and I-D how much time they spend dealing with bullshit each day. If you truely want to have a successful server, you have to be willing to put the time into it. If you want a server for your friends to play on or to run some server mod that isn't out there already then you can probably get away from all the nonsense.
I know none of you will read this but I'm not about to delete it now