I have to praise the Turbos for giving around 25-30 years reliable service and the constant starting and stopping too! I'm only 26 but I remember seeing the Turbos in Network South East and Thames Trains livery.
I know some people don't like the Turbos replacing Class 158's but I can think of these reasons why they're a big improvement over 150's and 158's...
1. Over double the number of seats in a 166+165 combination (5-car Turbo) than a 3-car 158.
2. (Unless one is feeling ill) Pretty much no smoke from the exhaust when at idle (in other words less pollution at idle) which amazes me because some newer diesels like tend to clag a bit. That's why Perkins-powered 158's are better for Birmingham New Street.
3. The 3+2 seating is useful for groups of 6 in particular.
4. More windows to be opened - handy on a hot day!
5. I guess faster boarding.
6. The 2+2 seating in the former First Class sections give a very spacious feel.
7. Better reliability I sense.
Also if anyone felt like I did during the last week of August a few weeks ago then you'd rather a seat in a Turbo than stand on a 158.
From travelling on Turbos on this route I have found:
1. 5 cars better than 3 cars but not a great deal of services seem to operate at 5 cars, and those that do seem to separate at Westbury and you always get people needing to get into the front carriages
2. Haven’t noticed many exhaust issues on 166s, but there again I haven’t on 158s either. 150s on the other hand...
3. I’m not sure how many groups of 6 there are travelling together, I use the route every day and maybe Friday and Saturday nights, but most of the time it’s solo passengers, two or small groups of 3 or 4.
4. There are more windows that open, but in reality they don’t, there are commonly some which can’t be opened because the locks are damaged or the restrictors have snapped off.
5. Boarding is faster
6. The 2+2 sections are great but always full
7. Reliability still seems hit and miss. I think there are less overall severe delays but I’m not sure that’s down to just the stock.
So IMO boarding and capacity are the major advantages of Turbos, but comfort and the overall passenger experience on 158s are better.
In summer, I have no problem with using a 150 on the route. The seating is good and lots more opening windows!