I had the same concerns way back in 2006 for my first UDM.
After much consideration, I opted for a easier but proven robust M43 for my E46. Since it was a year 2000 reg 2004, I took the liberty to get to know the brand and the beauty of the ultimate driving machine.
Owning cost throughout the years (until I had to sadly released it to a new owner here) was more of a wear & tear replacement issues. This was with the intention of a trouble free ownership. That set me back approx RM20k over 5 years.
I had no issue with reliability then, only off course it's just a 318 M43, I wasn't going for power. One thing for sure, FC was very good. This was the entry level BMW for me then. Additional RM20K on upgrades/accessories. It was a prefacelift stock condition and I did a conversion to facelift with original parts. It was a journey well learn with times of in & out of workshop!
Description that I've kept record on it so far...
Ride : E46 TiAg Racing Silver ( Euro Specs ) yr2000, reg2004. Mileage approx 100K miles. Lube service cycle every 5k miles and gear oil every 35k miles.
Engine & Performance : M43, Racecraft BMC CAI, AC Schitzner Rear Sport Silencer, 3M Injector Cleaner, Cruise Control
Lube & Petrol : 5W 40 Fully Synthetic Castrol Edge Sport
Brakes & Suspension & Handling : Eibach, Boge 6 potters (Sachs), EBC Rotors Front & Rear Grooved/Dimpled, BMW Black Caliper Covers, Goodridge Brakeline Kit with EBC Dot 4 Brake Fluid, Authentic AC Schitzner Anti-Roll Bar kit - 27mm front, 20mm rear
Wheels & Rims : 225/40/18 - All round (fronts are new, rear 70%), BMW E92 ///M3 18"x8.5 style rims
Exterior : BMW Original ///MtechII Bodykit Wrap Around with Authentic AC Schitzner Rear Diffuser, Authentic AC Schitzner Mirrors, AC Schitzner 3pcs Rear Spoiler, AC Schitzner Roof Spoiler, Club Sport Splitters, ///MtechII Carbon Fibre Brake Duct Cover, Black Out Kidney Grills, Silver Matt Trim Headlites Inserts, AL Headlites Clear Lense Cover, M Power Reg Black Surrounds, Carbon Fibre BMW Hood & Trunk Emblem, Original BMW Facelifted Parts (hood, fenders, lights)
Interior : ///M3 Tri-Color, MultiFunction Steering with SMGII F1 Paddles Retrofit, AC Schitzner Door Sills, AC Schitzner E-Brake, AC Schitzner Gear Knob, AC Schitzner Pedals & Foot Rest, Siver Gauge Rings, Silver Interior Trims with matching Silver Armrest
Lightings : OEM BMW Bi-Xenons Projectors with AL Ballast on D2S 4300K/Hi-Beam Philips Ballast on H7 6000K, Silver Vision Solaris Bulbs on front white markers and rear signals, CCFL Angel Eyes Vr 2, Smoked side markers, Facelifted BMW Original Lights, LEDs on Rear Trunk M Power Reg Black
I.C.E. : OEM BMW 16:9 Widescreen with CD dash and BMW 6 Disc CD Changer, /////Alpine V12, 4 Channel Amp MRV-F345 with Front /////Alpine SPR-17LS Component Speakers 350watts, /////Alpine SPS-17C2 Coaxial 2-way 250watts Rear Speakers System, Multimedia : DVD 6 Disc Changer with TV in Motion enabled
Sat Navigation : OEM BMW 16:9 Widescreen with CD dash, MKIV DVD ROM, Radio Tuner, TV Tuner, Retrofit Harness, GPS Antenna, Mal & Sin Map, Reverse Camera
Security : Stock Immobilizer and OEM Alarm
Option of split screen
And full screen (perspective view available)
I bet it's running strong today. Good luck shopping...!