I was on O2 LLU until I decided to get FTTC. For the same reasons as you are wondering about whether to stay with a niche provider, (I assume you mean IDNet), I in fact did go to IDNet on their Home Starter Fibre. Paid the year up front so it worked out at £23.82pm in effect, rather than the monthly £28.nn.
As you say - no problems whatsoever. But at the end of the 12 months I set to thinking, purely because that was more and more looking very expensive.
Narrowed it down to Infinity or Plusnet. A single phone call to each emphatically decided it. Plusnet had to think a bit about my questions but talked sense, the BT guys just spouted rot.
Eleven months into my 18 month contract with Plusnet I have just restarted the 18 months as a result of upgrading to the new Unlimited package. I have no regrets at all about leaving IDNet, flawless though they were. In my case, if not some others, Plusnet have also been flawless.
In case you haven't come across it in the extremely extensive (and sometimes bewildering so) Plusnet Help and FAQ systems, in the event of your being unhappy with Plusnet you can terminate your contract early at £5.75 per outstanding month not the full £19.99. (If within the first 12 months of it you also have to pay for the "free" router if you took it - its wireless is poor and mine is sitting gathering dust as a spare).
Plusnet have had a lot of complaints since the end of December about people ordering the Unlimited 80/20 package and being connected on 40/10 (but still unlimited as far as I know). This was a bug in the ordering system from when the unlimited package was introduced on 19 December 2012, causing the wrong speed product to be ordered from Openreach.
The bug has been fixed, but a few of the bad orders are still awaiting installation by Openreach, and it appears better to let them go through then do an upgrade (24-48 hours on request - or automatic at some stage) rather than Plusnet cancel and re-order thus losing weeks.
So don't worry about any of those reports.
I hope that helps.
My broadband basic info/help site - www.robertos.me.uk
| Domains,website and mail hosting - Tsohost
Connection - Plusnet
UnLim Fibre (FTTC). Sync ~ 54.3/15.4Mbps @ 600m. - BQM
"Where talent is a dwarf, self-esteem is a giant."
- Jean-Antoine Petit-Senn.
Allergy information: This post was manufactured in an environment where nuts are present. It may include traces of understatement, litotes and humour.