Yes get one - hunt around and get a good deal and you can get better than entry level for £150.
There are a few on here who quite rightly say get out and cycle outdoors - apart from snow and ice there is no excuse. The answer to that is - will you come round and baby sit because I can't go out out and leave two kids in bed and dinner in the oven whilst I go out and bike.
If you have the space for a permanent set-up they can be very quick. Tri-shorts, t-shirt, socks bike shoes on, pedal. No soaking wet overshoes at the end: three times a week + wet running kit and swimming kit (slightly damp). Plus no traffic lights, roundabouts, give ways, downhills - they are an efficient way of training.
So they can be worthwhile if ability to cycle outdoors is restricted, access to good training roads is restricted, and you can make yourself suffer.
M..eface