B737 First Officer inbound to LAX did not care for ATC vectoring methods and associated altitude restrictions.

Narrative

We were cleared for and flying the ILS 25L into LAX. At approximately 20 NM from touchdown we were asked by SOCAL approach if we could see traffic at the 10:00 to 11:00 position. Since we were in IFR conditions (OVC 009) and we could not see numerous aircraft in that direction we did not acknowledge seeing the aircraft. Shortly after that; while we were descending on the approach; the Controller directed us to level off at 5000 FT and continued to vector the aircraft across our nose -- we could not believe what we were seeing in IFR conditions. When the Controller felt we had enough clearance he then told us to slow to approximate 150 KIAS and then descend to 4000 FT and then 3500 FT. At about this point we had gotten about 2 dots above the glideslope. Fortunately the Captain was already slowing and had the gear down so we could slow and descend as quickly and as safely as possible. At some point before getting to 3500 FT and after the aircraft they were vectoring across our path was clear (we hoped); we were recleared for approach; it was about at that time that I commented to the Controller that I did not care for his vectoring. To our amazement after talking to the Supervisor once on the ground; SOCAL approach was more concerned about my comment than the fact that they were asking aircraft in IFR condition; flying IFR approaches to deviate from the approach so they could vector aircraft across the final approach flight path. Once again; we were only able to avoid going around because of the Captain's knowledge of how to fly the B737 and using his positional awareness. Should not have made the comment; but it was an unsafe practice; which they say they do all the time -- haven't seen it in 10 years of flying into LAX.