Short answer up front: Yes, election conditions in Ukraine improved after the Orange Revolution, according to independent observers.
The OSCE is one of the gold standards for independent observers of elections, and has been invited to observe all elections in Ukraine since the 1990s. Their reports are all available on the web-page dedicated to Ukrainian elections. Those web pages also contain significant additional information.
Elections Prior to 2004
Elections prior to 2004 were problematic at best, with major shortfalls. In 1999, for example enter link description here, the observers noted:
The Law on Elections of the President of Ukraine was adopted on 25 March 1999.... [But] selective interpretation and enforcement of legal provisions at various levels of the State structure prevented the uniform application of the law. As a result candidates were not competing on a level-playing field in the pre-election period, and the election disputes and appeal procedures generally did not provide the complainants with effective means to seek redress prior to the election.
In 2002 the observers wrote:
While Ukraine met in full or in part a number of commitments such as universality, transparency, freedom and accountability, it failed to guarantee a level playing field, an indispensable condition to ensure the fairness of the process.
The 2004 election was a pivot point for Ukrainian democracy. The first vote, and the second vote were not truly fair, but the vote called after the "Orange Revolution" showed a shift in attitude by the Ukrainian government towards democratic reform. At the time observers wrote:
The 2004 presidential election in Ukraine was a highly competitive contest, which offered voters a genuine choice between a plurality of candidates. While the 31 October (first round) and 21 November (second round) votes failed to meet a considerable number of OSCE Commitments, Council of Europe and other international standards for democratic elections, the 26 December repeat second round vote brought Ukraine substantially closer to meeting them. The improvement was most clearly demonstrated in the media coverage, the overall conduct of the campaign and the transparency in the CEC performance, including the immediate publication of polling station results. These measures stand in stark contrast to the previous votes, and demonstrate that when a clear political will is evident to conduct an election in line with OSCE commitments, much can ultimately be achieved in a short time period.
In essence, immediately after the Orange Revolution, conditions improved.
From 2004 to 2012, Ukrainian elections have received mostly positive reports from the OSCE. In 2006, 2007 and 2010 the OSCE observers reported that the elections were mostly in line with standards for free elections. In each case, however, the observers did report that problems continued to exist, and recommend improvements. The most severe rebuke came in the 2007 report which warned:
However, the IEOM also noted some areas of concern, including some recent amendments to the election law, the inadequate quality of voter lists (VLs), and possible disenfranchisement of voters who crossed the state border after 1 August 2007.
In 2012, the quality of Ukrainian elections declined dramatically. The OSCE observers reported:
...certain aspects of the pre-election period constituted a step backwards compared with recent national elections. In particular, these elections were characterized by the lack of a level playing field, caused primarily by the abuse of administrative resources, lack of transparency of campaign and party financing, and the lack of balanced media coverage. While the voting and counting processes on election day were assessed
positively overall, the tabulation of results was negatively assessed in nearly half of the electoral districts observed. Post election day, the integrity of the results in some districts appeared to be compromised by instances of manipulation of the results and other irregularities, which were not remedied by the Central Election Commission (CEC) or the courts. "
This is the election which sparked the Euro-Maidan movement. Tensions which led to violence in the Eastern Provinces continued during the 2013 elections, but those elections were reported as free and fair for the provinces which participated. The ongoing conflict has continued to mar national elections, but in both2014 elections and in 2015, reports by the OSCE were positive.