Why must the topic "Honda Wave 125x"? As if you made up your mind to buy it, just that your not confident and seek others opinion just to soothe your feeling/ doubt. Maybe it would be more open to put "recommended bike for me?" then u can put other info such as budget, usage @ distance covered per day, your weight etc etc. So can get many other opinion from multitude dimension/perspective.
To answer your question:
Wave X among the most efficient bike in terms of its Fuel Consumption. It can go 50-55km/L compared to wave 100 or wave 110 which cant get that measurement (subject to riding style). But good FC comes with a price, its not as fast as other motorcycle in the same class.
Acceleration is good (though not as good as most Yamaha's), top can reach minimum 120kmh (after break in). This reading is based on 75Kg rider. With total weight of more than 100kg, u'll feel sluggish and top reduce to 110kmh.
Engine, its durable. But depend on how you maintain it. Got 1 friend of mine, really maintain it well(38,000++ KM), change Engine oil every 1500km/month. But when i test ride the bike, i can tell it's sluggish. Then i changed it with semi-syn and problem solved. So i assume this bike better off with at least semi syn.
If you really made up your mind to get wave X, i don't see any problem with that (unless your a speed lover). Gud luk