Taking your questions in order:-
LLU is fine, though slightly affected in my case in the last three or four days. Although at non-heavy times I still get my expected 5.9-6.1Mbps I can at some times be as low as 5.1Mbps. As in the past, Be have announced that network enhancements are on their way and these have always happened.
The last lot were in mid-December and would have been based on growth trends continuing as normal. The Entanet influx is bound to have upset that forecast.
Prior to the last lot Access was suffering as well and improved at the same time, presumably as something the other side of the servers from users got upgraded. Anyone's guess on that this time, but not relevant to your friend.
So I would say he/she should join O2.
Reasons for
leaving Newnet.
Migration details here, including getting a free SIM.
If I ever leave which on current form is unlikely, (but like most people saying that about their ISP things can change quickly - I used to say the same about Newnet, but my usage suddenly started growing), by then IPSream will probably be dead and the packages on WBC and WMBC could have different joining terms. In any case, at the moment Newnet at least still have a one-month contract and no joining charge from LLU and there may be others, and freeola still have a low charge.
In any case, with the money saved on O2 I see no drawback if I have to pay a joining fee to a new ISP if necessary.
On O2 LLU (Standard) even with no huge speed gain the freedom from even thinking about how much I have used in the month is a great relief, and the absence of the IP Profile pain after a slightly low sync and then four or five days for it to recover is sheer bliss.
Initially I was using the O2 Box. That was fine - giving me higher speeds 24/7 than IPStream/Newnet, but lower in the evenings and night than day-time as I always got a re-sync due to noise and lost about 300-400kbps. Recovered immediately by re-sync'ing manually next morning.
I have now got a NetGear 834N and can tweak that to give even higher speeds, as above, and been sync'ed since 10am 5 Jan.