Having tried 1st class, when the previous "Great Escape" was on, then I would say that it is marginal as to whether 1st class on LM is better. The seats seem hard and narrow compared to 2nd class and indeed, it is often easier to spread out in 2nd rather than 1st. Unless of course, as stated above,one rates the privacy of 1st and the almost guaranteed chance of getting a seat.It depends. If you're out on the mainline routes, want a guaranteed seat and table, and want a comfy seat then yes you could say it is good value. Doing 3.5 hours on a 350/2 to Crewe is NOT particularly brilliant, and a couple of turns a day still end up being a /2. Near peak times, it is going to get busy so FC will give you a seat for sure!
If you're wanting to do the local routes, round Snow Hill etc then probably not worth it at all!
Having said that, I only travelled north of Tamworth, so I cannot say from experience, how full the trains get in the London area.
Perhaps LM will change the seats in 1st at some point, to be wider, softer and in a 2+1 formation, rather like the ex Midland 170's were, BEFORE arriva ripped them all out !